| 摘要 |
PROBLEM TO BE SOLVED: To easily drill a work at low cost in drilling the work even when a surface of the work such as a forged part is a roughened surface. SOLUTION: This drill 1 is furnished with a drill body 4 and a shank 6 arranged on a shaft center 5 of this drill body 4 and integrally formed with a base part of this drill body 4. A diameter D2 of the shank 6 is made larger than a diameter D1 of the drill body 4. The other helical flute 17 continued to a helical flute 9 of the drill body 4 is formed on the shank 6, and a bottom part of the other helical flute 17 is made almost in the same shape and in the same size as the helical flute 9. An outer edge 18 except for the other helical flute 17 on each part cross section in the axial direction of the shank 6 is positioned on a virtual circle with the shaft center 5 as its center. COPYRIGHT: (C)2007,JPO&INPIT
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